Implement actions to build, test and upload Hakunapi packages to public Maven repository

[teezip]

Alternatives:

1. Maven Central
2. GitHub packages

Maven Central requirements and guides:

• https://central.sonatype.org/publish/requirements/
• https://dzone.com/articles/how-to-publish-artifacts-to-maven-central

About signing process and GPG keys (when publishing on Maven Central)

• https://docs.github.com/en/authentication/managing-commit-signature-verification/generating-a-new-gpg-key
• https://central.sonatype.org/publish/requirements/gpg/#distributing-your-public-key
• https://maven.apache.org/plugins/maven-gpg-plugin/sign-mojo.html
• https://www.simplify4u.org/sign-maven-plugin/

About group id on Maven Central

• https://central.sonatype.org/publish/requirements/coordinates/

The alternative 1 was selected, steps:

1. (OK) group id "fi.nls.hakunapi" registered on Maven Central
2. (OK) signing process tested with a test GPG key PR #15
3. signing process with a production GPG key
4. publish pre-release version of Hakunapi 1.0 on Maven central